Merge branch '2.2' into 2.3

* 2.2:
  corrected English grammar (s/does not exists/does not exist)
  [Process] Add more precision to Process::stop timeout
  [Process] Avoid zombie process in case of unit tests failure
  [Process] Fix #8739
  [Process] Add failing test for #8739
  [Process] Fix CS
  Fixed documentation grammar for AuthenticationManagerInterface::authenticate()
  [Validator] fixed the wrong isAbstract() check against the class (fixed #8589)
  [TwigBridge] Prevent code extension to display warning
  Use strstr instead of strpos

Conflicts:
	src/Symfony/Component/Finder/Shell/Command.php
	src/Symfony/Component/Process/Process.php

Author: fabpot

Templating/Helper/CodeHelper.php

@@ -131,7 +131,9 @@ public function fileExcerpt($file, $line)
                 }
             }
 
-            $code = highlight_file($file, true);
+            // highlight_file could throw warnings
+            // see https://bugs.php.net/bug.php?id=25725
+            $code = @highlight_file($file, true);
             // remove main code/span tags
             $code = preg_replace('#^<code.*?>\s*<span.*?>(.*)</span>\s*</code>#s', '\\1', $code);
             $content = preg_split('#<br />#', $code);